In this installment, we look back at designs from previous October editions of Elektor Mag. Whether you are a pro or newbie to engineering, we have something for everyone: neural networks, the “Tube Clipper,” the “TV Scope,” and more.

Understanding the Neurons in Neural Networks (Part 1): Artificial Neurons (Sep/Oct 2021)

Artificial intelligence (AI) is a hot topic in engineering today, but Elektor has been covering AI, machine learning, and related projects for several years. Back in October 2021, we kicked off a series titled "Understanding the Neurons in Neural Networks." In the first installment, we dove into artificial neuron research, a multilayer perceptron (MLP) software implementation, and more. 

"Early attempts at building a digital, or artificial, neuron turned to nature for inspiration. The biological neuron accepts inputs via its dendrites and passes on any resultant output through its axon to the axon terminals. The decision of whether to emit a stimulus via the output, known as the neuron firing, is undertaken using a process called activation. Should the inputs conform to a learned pattern, the neuron fires. Otherwise, it does not. It can quickly be seen that, with chains of interconnected biological neurons, very complex patterns can be recognized." Check out the full article to learn more.  
Neural network - engineering insights
What is a neuron anyhow?

Candle2light: Luminous Efficacy Booster (Sep/Oct 2017)

Back in 2017, Elektor presented an engineering project that quickly became a classic. The design converted heat from a candle's flame into electrical energy — enough to light a small lamp. Check out the neat design!  

"The thermoelectric generator for this project consists of two 40 x 40 mm TEC1-12706 Peltier modules (Figure 1) connected in series. They are clamped between two heat sinks by springs. This assembly is mounted above a tea light holder and can be adjusted in height. The bottom heat sink measures 40 x 40 x 10 mm and is intended to distribute the heat from the tea light evenly over the full surface of the Peltier modules. The top heat sink, which is twice as high and therefore has much lower thermal resistance, is cooled by a fan to keep the cold side of the Peltier modules as cool as possible."
Peltier project
Convert heat from a candle's flame into electrical energy!
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The 5532 OpAmplifier (Oct 2010)

The (NE)5532 is widely known. Did you know that a power amplifier can be made by connecting several 5532s in parallel? What about more than 30? Take a look at the article to learn more about the interesting design.   
5532 opamp
Engineering tip: you can make a power amplifier by connecting several 5532s in parallel.
It might sound over the top, but Elektor showed in October 2010 that the result can be a simple amplifier with excellent linearity and "the power-supply rejection and the inbuilt overload protection of the 5532, which reduces the external circuitry required to a minimum." The amplifier is built on a double-sided through plated circuit board.

Tube Clipper: Audio Processor With Valves (Oct 2001)

Many audiophiles like valve sound, but don't want to spend big money on a valve amplifier. The Tube Clipper was an interesting alternative. It was a effect/preamplifier that produced the valve sound, but it used low-voltage valves and needed no voltage higher than ±12 V. It was an ideal introduction to valve technology.  
The Tube Clpper - An engineering solution
The Tube Clipper
"The idea behind the Tube Clipper is to limit the audio signal at a given preset maximum level. Valves do this in a rather gentle way: they do not limit excessive voltages as ‘hard’ as transistors do when driven into saturation, but rather as the voltage rises towards the limit value, the valve begins to clip gradually. Hence we obtain the desired smooth curve."

Distortion (Fuzz) Unit for Electric Guitars (Oct 1997)

This distortion ("fuzz effect") unit produces soft clipping, which generates an effect similar to that produced by valve amplifiers. Soft clipping means that the signal isn't allowed to exceed a certain voltage level. Users can insert this design between a guitar and its amplifier. 
Distortion unit
Distortion unit
"The imitation of the performance of a valve (tube) amplifier, without using a single valve (tube) requires an inordinate amount of well-thought-out filtering," the designer wrote. "This means that the present unit contains rather more electronics than most other fuzz boxes ... However, the end justifies the means, but, all the same, with just three ICs, four potentiometers, and a small number of resistors and capacitors, the circuit is not that extensive."

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Computer-Controlled Teletext System (Oct 1989)

In October 1989, Elektor presented an experimental system that enabled users to load Teletext pages — including those not normally accessible on a TV with a Teletext decoder — into a PC. Check out the block diagram nearby.  The function of the controller card is to respond to instructions received on the RS-232 link to a PC and to return Teletext information to a host computer. All the timing and protocol requirements needed to transfer information on the I2C bus are handled by an 8051-based controller card.
PC-controlled Teletext system
PC-controlled Teletext system
“The Teletext decoder described here can access all definable pages and rows and make them available to a personal computer (PC) for analysis. The design is split into three units, two of which will be described in detail in this article. These two units are a Teletext decoder and a data and control interface connected to a PC's RS232 port. The third unit in the proposed system is a TV tuner.”

Plug-In EPROM Programmer (Oct 1981)

“Program 2716s the easy way!” Elektor wrote in 1981. In October of that year, the team presented a circuit for loading programs (or other data) into 2716 EPROMs. According to the designer, it used only one 555 timer, one TTL IC, and a few other components.  
EPROM programmer - engineering in 1981
The plug-in EPROM programmer
“In practical terms, the whole procedure for programming a 2716 EPROM is as follows: 

•    Insert the auxiliary circuit in the EPROM socket and plug the (erased) EPROM into the top; connect the R/W, OPACK and 25 V lines with flying leads.
•    For the 2650, the program … can now be run: it will load up to 256 bytes from a specified address and transfer them to the specified EPROM address. Obviously, this program can be modified or relocated according to the desired application.
•    Disconnect the flying leads, remove the auxiliary circuit and insert the EPROM in its intended socket. Job done!”

TV Scope: Basic Version (Oct 1978)

Back in 1978, you couldn't just order an inexpensive oscilloscope on the Internet and have it shipped to your home in a matter of hours. At that time, oscilloscopes were beyond the reach of many electronics enthusiasts and students. "A major proportion of the cost of an oscilloscope is accounted for by the cathode-ray tube and its associated high-voltage power supplies," Elektor pointed out at the time. A workaround was to build your own engineering solution with a little help from Elektor! By using a TV set as the display, the "TV Scope" enabled readers to construct an oscilloscope for a very modest outlay.  
TV scope
The TV Scope

“The main board accommodates a number of circuits which perform a variety of different functions. There is the crystal oscillator, the timebase circuit, which is also responsible for generating the graticule, and the white-level pulse generator which produces the actual trace on the screen,” Elektor explained. “A 4.433 MHz crystal is used, and since this type is commonly found in a number of colour TV sets it is both reasonably cheap and easy to obtain.”

More Engineering to Follow!

Want more? During the next few months, we will highlight other classic Elektor articles, engineering tutorials, and projects. Please share your thoughts in the comments section below. The engineering never stops!

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